1. Field of the Invention
The present invention relates to a pellicle that is used in a photolithography process when producing a semiconductor device and such, particularly relates to a pellicle frame for constituting the pellicle.
2. Description of the Related Art
In the production of a semiconductor such as LSI and super LSI or in the production of a liquid crystal display panel and such, there is a photolithography process in which a patterning is performed by irradiating a semiconductor wafer or a liquid crystal display panel with a light.
If dust is adhered to an exposure original plate to be used for patterning (called a mask for lithography, a reticule, or the like), there are caused problems that the dust absorbs light or refracts light, thus, transferred pattern may be deformed, its edge may be rough, and also its base may be soiled to be black, resulting in degradation of dimension, quality, appearance or the like.
For preventing dust from adhering to the original plate, the works relating to lithography are usually done in a clean room. However, since it is difficult to always keep an exposure original plate clean even in the clean room, a pellicle for avoiding dust is generally attached to the surface of the exposure original plate.
FIG. 2 is a schematic sectional view showing a fundamental constitution of a pellicle 11, where a pellicle film 13 which transmits the light for exposure is adhered to one end face of a pellicle frame 12. For the pellicle frame 12, materials such as aluminum alloy of A7075 and such, stainless, polyethylene, or the like are used, and for the pellicle film 13, there is used a transparent film which consists of, for example, nitrocellulose, accetylcellulose, fluorinated polymer, or the like and well transmits the light used for exposure (See, Japanese Patent Application Laid-open (kokai) No. 58-219023).
When the pellicle film 13 is adhered to the pellicle frame 12, a volatile solvent is applied between the frame 12 and the film 13, and air-dried (See, Japanese Patent Application Laid-open (kokai) No. 58-219023), or the frame 12 and the film 13 are adhered through an adhesive 16 such as acrylate resin, epoxy resin, or the like (See, Japanese Patent publication (kokoku) No. 63-27707).
Moreover, at the lower end face of the pellicle frame 12, for adhering it to the exposure original plate, there is provided an adhesive layer 14 consisting of polybutene resin, polyvinyl acetate resin, acrylate resin, or the like, and an adhesive layer-protecting liner 15 for the purpose of protecting the adhesive layer 14.
By adhering such a pellicle 11 to the exposure original plate, dust does not adhere directly to a surface of the exposure original plate, but to the pellicle film 13. And if the focus is adjusted to the pattern of the exposure original plate when performing the lithography, dust on the pellicle film 13 can be prevented from affecting the transfer.
On the other hand, if a pattern formation surface of the mask (the reticule) is hermetically sealed by the pellicle, it is feared that there are caused problems such that the pellicle film is swollen to contact with a portion of the exposure device by lowering of the surrounding barometric pressure, or the like. Accordingly, there is suggested a pellicle that by forming a vent and installing a filter at a side surface of the frame, foreign materials such as dust can be prevented from infiltrating and at the same time barometric pressure can be adjusted (See, Japanese Utility Model Application Laid-open (kokai) No. 61-41255). Furthermore, for excluding the affection of gas existing in the exposure environment, it is also suggested to provide a chemical filter containing titanium oxide and such (See, Japanese Patent Application Laid-open (kokai) No. 2003-57804)
In recent years, the pattern rule of LSI has become finer to sub-quarter micrometer, along with this, wavelength of the exposure light source has become further shorter. KrF excimer laser (248 nm), ArF excimer laser (193 nm), and further F2 laser (157 nm) are being used as well as g-ray (436 nm) and i-ray (365 nm) by a mercury lamp that have ever predominated.
Along with wavelength of the exposure being shorter as described above, energy that a light has becomes higher naturally. In the case of using a high energy light, gaseous substance existing in the exposure atmosphere reacts easily as compared to a light with comparative long wavelength used conventionally, thus a possibility that reaction products are generated becomes drastically higher. If such reaction products are adhered to the mask, it is feared to affect fine pattering.
Accordingly, it has been desired that the gaseous substance is reduced as much as possible, the reticule is sufficiently cleaned, generation of gases from components of the pellicle, namely a reticule adhesive layer (sticking layer), a film adhesive, a coating agent coated on the inner wall of the frame, or the like are lowered. And improvement is being made.
However, even though cleaning of the reticule and lowering of the gas generation from components of the pellicle are improved, there are cases that cloudy foreign materials which are referred to as haze are generated on the mask substrate. The generation of such haze causes degradation of process yield in semiconductor manufacturing.